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Study on the Preparation of Silica and Activated Carbon from Rice Husk Ash

Author: LiCai
Tutor: HuQiuLin
School: Wuhan Polytechnic University
Course: Cereals, Oils and Vegetable Protein Engineering
Keywords: rice husk ash water glass silica activate carbon
CLC: TQ424.1
Type: Master's thesis
Year: 2011
Downloads: 51
Quote: 0
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China is rich in rice husk which is a by-product of rice process. Restricted by its own characteristics, rice husk has only be en used as a kind of primary fuel for a long time, and a large number of RHA remains even after this procedure. RHA needs to be handled promptly, if not, which will have a negative effect on production and environment of rice processing enterprises. In this paper, we use the rice husk ash provided by Zhong Xin Energy Co. Ltd as the raw material, preparing water glass by alkali first, and then go through all the steps of filtering, washing and concentrating to obtain a certain modulus and mass fraction of water glass. Then took the water glass as raw material, prepared silica by precipitation method, activated the carbon residue to prepare high methylene blue adsorption of activated carbon. This method not only utilizes waste, protects environment and saves resources, but also has significant economic and social benefits.In this study, the first step was reaction between alkali and rice husk ash, and dissolving the silica in the RHA in the form of water glass. Then we discussed each of the major factors which affect the reaction under atmospheric pressure and 98℃. We explored how Liquid ratio, alkali concentration and reaction time affects the dissolution rate of silica and the modulus of sodium silicate and found out The best reaction condition is: 5g/40ml for ratio of solid and liquid, 2mol/L for alkali contration, 4h for reaction time, which can result in 91.8% of leaching rate of SiO2, a fairly high rate.Then, water glass is used as raw material to prepare high purity and uniformly dispersion of silica by adding surfactants and ethanol in the reaction system and ammonium chloride as the precipitating agent is used instead of commonly used sulfate to precipitate silica. The dispersion of the silica prepared by polyethylene glycol 6000, cetyltrimethylammonium bromide and sodium polyacrylate as surfactant are compared. Influences of the reaction temperature, chloride concentration and the reaction and point pH value on the silica purity and dispersion are respectively disscussed. Based on the single factor experiments and analysised by RSM, The optimum conditions of preparation of silica are determined: polyethylene glycol 6000 is used as surfactant, volume ratio of ethanol and water glass is 1:10, reaction temperature is 43℃, ammonium chloride concentration is 1.4mol/L, reaction end point pH value is 9.0 and the purity of silica prepared under the optimum conditions is 95.37% . Measured the characteristics of the product, test result is completely contented various index of GB/T 3061-1999.The high adsorptive activated carbon was made from the filter residue abandoned by the preparation process of water glass though chemical activation. The KOH was considered as the best activator by comparing the activated effect of products which was produced by using different activator (K2CO3, KOH, ZnCl2 and H3PO4) . The optimum technics parameters were temperature of 650℃, time of 20min and concentration of KOH 2.5mol/L. Under the condition, the methylene blue value was up to 15.3mL/0.1g which satisfied the standard of LY/T 1281-1998.

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CLC: > Industrial Technology > Chemical Industry > Reagents and the production of pure chemicals > Adsorbent > Activated carbon
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